Battery power supply,maintenance free

ABSTRACT

A power supply which automatically provides the necessary maintenance cycling for secondary batteries according to a predetermined schedule is disclosed. The power supply is designed to eliminate the detrimental effects of long idle periods during which the battery is not used. This system will, at a predetermined time, or at the end of a predetermined period, cause the battery to go through a discharge-charge cycle. Several embodiments of the invention are disclosed.

United States Patent [191 Mauch et a].

' 1 Mar. 12, 1974 BATTERY POWER SUPPLY, MAINTENANCE FREE Inventors:Robert E. Mauch; Robert I.

Sarbacher, both of Santa Monica, Calif.

Assignee: John C. Bogue, Santa Monica, Calif.

Filed: Dec. 27, 1971 Appl. No.: 212,178

US. Cl 320/14, 320/21, 320/44 Int. Cl. .t H02j 7/00 Field of Search320/14, 21, 43-45;

References Cited, UNITED STATES PATENTS 9/1970 Dickfeldt et a1. 320/1412/1968 Kosa et al. 320/14 X 1/1969 Wilson et a] 320/14 PrimaryExaminer-D. F. Dug'gan Assistant Examiner-Robert J. Hickey Attorney,Agent, or FirmWitherspoon and Lane [57] ABSTRACT A power supply whichautomatically provides the necessary maintenance cycling for secondarybatteries according to a predetermined schedule is disclosed. The powersupply is designed to eliminate the detrimental effects of long idleperiods during which the battery is not used. This system will, at apredetermined time, or at the end of a predetermined period, cause thebat: tery to go through a discharge-charge cycle. Several embodiments ofthe invention are disclosed.

16 Claims, 5 Drawing Figures PATENTEDIAR 12 m4 SHEET 1 BF 2 BATTERY IOSENSING I COULOMETER AND RESET SWITCH CONSTANT CURRENT REGULATOR FIG.

FIG. 2

INVENTORS: ROBERT E. MAUCH.

R. SARBA CHER.

PAIENTEUHAR 12 m4 3; 796; 940

SEQUENC/NG I B3 I 7 I 82 Bl SWITCH T/M/NG 5O 62 SEQfJE CING SINGLE J NCELL CHARGER D/SCHARGE BELOW 64 MONITOR NORMAL F I G, 4

CELL

/N0/CAT0R F T T '1 76 :NCELLS:

SWITCH VOLTAGE SENSING A FIGS 0 B INVENTORS. ROBERT E MAUCH. RsARBACHER.

1 BATTERY POWER SUPPLY, MAINTENANCE FREE BACKGROUND OF THE INVENTIONThis invention relates to maintenance cycling of secondary batteries ina power supply; and, more particularly, to a power supply that providesautomatic maintenance cycling of its secondary batteries.

Storage batteries which are maintained in a charged state continuouslymay show marked capacity deterioration. This problem can be avoided byperiodically cycling the batteries through a dischargecharge cycle. Atpresent this periodic cycling is usually accomplished by manualmaintenance scheduling. Such scheduling is costly and ofteninconvenient.

This invention provides the maintenance cycling automatically. Thebatteries are periodically discharged and charged automatically. Nohuman operation of any kind is necessary with this invention after ithas been installed in the power supply. The battery or batteries orcells of a battery are automatically cycled at periodic intervals.

SUMMARY OF THE INVENTION This invention provides an automatic system formaintenance cycling of secondary batteries that are continuouslymaintained in a charged condition. The battery or batteries areautomatically removed one at a time from the charger, discharged andplaced back across the charger for recharging. This cycling is carriedon periodically. The time between discharge cycles is controlled by acoulometer or the like.

In one embodiment of the invention, power cannot be supplied to a loadduring cycling. In another embodiment power is available to the load atall times, including the times at which a discharge cycle is takingplace. In yet another embodiment of the invention, the individual cellsof a battery of cells are periodically discharged and then recharged. Ifa cell becomes defective an indicator is provided to indicate that adefective cell exists. However, the circuitry is such that the batterycan still be operated with only a slight effect until the defective cellis replaced. With the single cell cycling embodiment power is alsoavailable to the load at all times.

In addition to the maintenance cycling embodiments, a sequencing systemfor the single cell embodiment is disclosed. In this sequencing systemadditional cells are added as needed to maintain the voltage availableto the load at a particular value. Thus, for example during thedischarge cycle of a cell another cell not normally needed to maintainthe desired voltage will be automatically added to the battery.Similarly, if one or more cells become defective one or more of theadditional cells will be added to the battery.

DESCRIPTION OF THE INVENTION A full understanding of the invention canbe obtained from the following detailed description when read inconjunction with the annexed drawing in which:

FIG. 1 shows an embodiment of the invention in which power is notavailable during the cycling period;

FIG. 2 is a schematic diagram showing preferred circuitry for carryingout the invention as shown in FIG.

FIG. 3 shows an embodiment of the invention in which power is availableduring the cycling period;

FIG. 4 shows a second embodiment of the invention in which power isavailable during the cycling period; and

FIG. 5 shows a control network ideally suited for use with the system ofFIG. 4.

DETAILED DESCRIPTION OF THE INVENTION When power is not required fromthe battery during the cycling period, the system shown in FIG. 1 may beused. This system contains a battery 10 in series with a switch 15.Battery 10 and switch 15 are connected through the terminals A and B toa conventional charger and load, not shown. The charger maintainsbattery 10 in a fully charged state. The constant current regulator 11and the coulometer 12 comprise a timing network which measures theamount of time that the battery has been on charge, or that the systemhas been active. At a predetermined time, say 6 months, the coulometerreaches its end point and the sensing and reset device 13 activatesswitch 15 which causes battery 10 to be disconnected from terminals Aand B and connected across the substitute load 14, thus discharging thebattery. During battery discharge, sensing and reset unit 13 resetscoulometer 12 to its starting point. At the end of the discharge timeswitch 15 returns to its normal position, disconnecting substitute load14 and reconnecting battery 10 accross the terminals A and B. At thistime the battery charger will return the battery to its fully chargedstate, thus completing the full discharge-charge cycle. With thissystem, power cannot be drawn from storage battery 10 while thedischargecharge cycle is in operation. It should be apparent thatadditional batteries can be connected directly in parallel with battery10. These additional batteries would be cycled simultaneously withbattery 10.

FIG. 2 is a schematic diagram showing circuitry ideally suited forperforming the functions of the various blocks of FIG. 1. In FIG. 2, theblocks of FIG. 1 are illustrated by the dashed lineboxes having the samenumerals. Thus, switch 15 is shown as being a single-pole, double-throwrelay 21. Relay 21 is normally in its closed position, as shown, exceptduring the discharge cycle. When switch 15 is closed, battery 10 isconnected to terminals A and B. In place of the electromechanical relayshown for switch 15, solid state switching devices or other suitableswitches could, of course, be utilized for this switch.

The components of the constant current regulator 11 comprise a standardform of constant current regulator wherein a zener diode 27 and aresistor 29 fix the potential of the base of the transistor 28. Thecollector current of transistor 28 is always such that the voltage dropacross the resistor 26 is always a fixed value and thus the currentdelivered to coulometer 12 is always a fixed value.

The element 31 of coulometer l2 maintains a low voltage drop until aftera given specific quantity of current has flown through it. When thisspecific quantity of current is reached the voltage drop across element31 abruptly rises. This voltage forward biases the base emitter junctionof the transistor 34 through the resisor 33 causing transistor 34 toactivate relay 21. The activation of relay 21 disconnects the battery 10from terminal A and connects it to substitute load 14.

In addition to the power drawn by load 14, power is also drawn frombattery through the resistor 38 to cause the negative side of thecoulometer element 31 to become more positive than the zener voltage ofthe zener diode 30, thus reversing the current flow through thecoulometer element 31. The resistor 32 connected to coulometer element31 is used for current limiting. This resets the coulometer preparing itfor the next timing cycle.

The current flowing through resistor 38 causes the transistor 36 to beforward biased through the resistor 37; thereby, turning on thetransistor 35 which holds relay 21 in the discharging position forbattery 10 until the voltage across the coulometer element 31 rises to avalue which terminates the current flow. When the current flowterminates relay 21 returns to its normal state, as shown in FIG. 2.

The circuit will also terminate battery discharge if the battery voltagefalls below the value which will not drive sufficient current throughresistor 38, thus protecting battery 10 from excessive discharge duringthe cycling period. Since the discharge period lasts for a specifiedperiod of time if controlled only by coulometer 12, an under capacitybattery would be excessively discharged if provision were not made toterminate discharge when battery 10 reaches a given voltage value. Thus,this system will not damage the battery 10 as it loses capacity withage.

FIG. 3 shows a second embodiment of the invention wherein two batteriesare used and only one of them is cycled at any given time. The terminalsA and B of FIG. 3 are connected to the batteries 40 and 41 through theswitches 45 and 42, respectively. The constant current regulator 47 inseries with the coulometer 48 and the sensing unit 49 function the sameas regulator 11, coulometer l2 and sensing unit 13 of FIG. 1, theoperation of which is fully described above. In response to signals fromsensing unit 49, either battery 40 is removed from terminal A andconnected to the substitute load 44 by means of switch 45, or battery 41is removed from terminal A and connected to the substitute load 43 bymeans of switch 42. Which battery is disconnected from terminal A andconnected to its associated substitute load is determined by thesequencing unit 46. Sequencing unit 46 is a common switching unit thatmerely first switches one of the batteries and then in response to latersignals from sensing unit 49 switches the second battery to itssubstitute load. During the next discharge cycle the first battery willagain be switched to its substitute load and so on in this alternatingfashion. Thus, the batteries 40 and 41 are alternately discharged duringsuccessive cycling periods. Only one battery is disconnected fromterminals A and B at any given time. Therefore, power is available fromat least one battery.

The block diagram of FIG. 3 may be implemented with the same type ofcircuit shown in FIG. 2. However, relay 21 of FIG. 2 would be replacedby a stepping type relay or other conventional stepping device toimplement sequencing unit 46 and thereby properly operate switches 45and 42. Of course, additional batteries and appropriate switches can beadded to the circuit.

FIG. 4 shows a block diagram of a system which will provide power duringcycling periods without the ne-. cessity of an additional battery.Additional provisions are shown for the maintenance of a highreliability battery system. As in the previous examples of thisinvention terminals A and B represent the connections to the chargingequipment.

The battery cells 8,, B and B are connected in series to form a batterypack of the desired voltage. The diodes 51, 52, 53, 54, 55, 56, 57, 58and 59 are inserted in the battery pack in a manner which prevents cellreversal of any one of the cells during discharge of the pack. Thetiming and sequencing control 60 may contain, as in the previousexamples, a coulometer and constant current regulator. At the pre-setspecified time, control 60, through the switch 61, initiates a dischargeof one of the cells B,, B and B At each timing cycle a different cellwill be discharged. As the cell is discharged the monitor 63 checks fora given capacity in this cell and if the cell does not meetspecifications the discharge monitor 63 activates the indicator 65.After the cell has been discharged it is brought back to full charge bythe cell charger 62. Thus, during any cycle period no more than one cellof the battery of the many cells 8;, B through B will be discharged andvery nearly normal power is available at all times. In addition, anydefective cell will be indicated within the cycle period. A defectivecell will not significantly affect the performance of the battery fromthe time it is indicated until it is replaced, since the diodes SI, 52and 53 act to shunt it. When the battery is originally designed for thepower supply, it may contain extra cells so that the loss of one or moremay have only a slight effect on the performance of the power supplysystem. The terminals C and D represent connections to the utility powerlines.

The sequencing system shown in FIG. 5 is ideally suited for use with themaintenance system shown in FIG. 4. The terminals A and B are theterminals of the normal battery charger, and in addition, a maintenancesystem of this invention as described above would be connected to theseterminals. The load is connected across terminals A and C in FIG. 5. g

The battery pack B through 8,, is maintained in a fully charged state bythe normal charger of the power supply. The voltage sensing unit 79monitors the voltage applied to the load between the terminals A and Cand causes switch 78 to select a tap point 81, 82, 83 and etc. from thebattery pack which will place a sufficient number of cells across theterminals A and C to maintain the desired voltage. If any cell shouldbecome defective switch 78 will select a higher tap from the battery soas to compensate for the defective cell. The bad cell will be shunted byone of the diodes 70 through 73, depending on which is the bad cell,thus allowing the remainder of cells of the battery pack to function Inormally. As the cells become exhausted, switch 78 will continue to addmore cells to maintain the proper voltage to the load. When thecell-pack is recharged the zener diodes 74 through 77 preventover-charge of their associated individual cell and therefore cause thecharging current to be distributed to those cells which have beendischarged.

In the FIG. 4 embodiment of the invention it is apparent that, the onecell can appear to be defective because it is going through itsmaintenance cycle. The sequencing system of FIG. 5 will compensate forthis maintenance cycle of a cell so that there is no apparent effect atthe load. The sequencing system of FIG. 5 merely adds another cell tomaintain the predetermined proper voltage.

While the invention has been described with reference to specificembodiments, it will be apparent to those skilled in the art thatvarious changes and modifications can be made to the embodimentsdisclosed without departing from the spirit and scope of the inventionas set forth in the appended claims.

What is claimed is:

l. A battery power supply automatic maintenance cycling systemcomprising:

a battery normally coupled across a battery charger;

a coulometer for measuring time coupled to said battery;

a dummy load; and

means responsive to said coulometer for automatically uncoupling saidbattery from said battery charger after a predetermined period of timeand coupling said battery to said dummy load to discharge said batteryand then uncoupling said battery from said dummy load and recouplingsaid battery to said battery charger after said battery has beendischarged for a predetermined period of time that is measured by saidcoulometer.

2. A battery power supply automatic maintenance cycling system asdefined in claim 1 wherein a constant current regulator is connected inseries with said coulometer.

3. A battery power supply automatic maintenance cycling system asdefined in claim 2 wherein said means responsive to said coulometerincludes a voltage responsive switch coupled to said battery, saidbattery charger and said dummy load such that said battery is coupled tosaid dummy load as long as a voltage is applied to said switch and iscoupled to said battery charger when no voltage is applied to saidswitch.

4. A battery power supply automatic maintenance cycling system asdefined in claim 3 wherein said coulometer provides a first voltage whensaid battery has been coupled across said battery charger for apredetermined period and a second voltage when said battery has beencoupled across said dummy load for a predetermined period of time andwherein sensing and reset means are coupled between said coulometer andsaid switch to provide a voltage to said switch to uncouple said batteryfrom said battery charger and couple said battery to said dummy load inresponse to said first coulometer voltage and to remove said voltagefrom said switch in response to said second coulometer voltage torecouple said battery to said battery charger' 5. A battery power supplyautomatic maintenance cycling system as defined in claim 4 wherein nopower is available to an external load during the time said battery iscoupled to said dummy load. 4

6. A battery power supply automatic maintenance cycling system asdefined in claim 5 wherein at least one additional battery is connectedin parallel with said battery.

7. A batterypower supply automatic maintenance cyling system comprising:

a first battery normally coupled to a battery charger;

a second battery normally coupled to said battery charger; timemeasuring means coupled to said first battery and said second battery;

a first dummy load; a second dummy load; and

means responsive to said time measuring means for automaticallyuncoupling said first battery from said battery charger after apredetermined period of time and coupling said first battery to saidfirst dummy load to discharge said frist battery and then uncouplingsaid first battery from said first dummy load and recoupling said firstbattery to said battery charger after said first battery has beendischarged for a predetermined period of time that is measured by saidtime measuring means, and for automatically uncoupling said secondbattery from said battery charger a predetermined period of time aftersaid first battery is recoupled to said battery charger and couplingsaid second battery to said second dummy load to discharge said secondbattery and then recoupling said second battery to said battery chargerafter said second battery is discharged and then after anotherpredetermined period of time again uncoupling said first battery fromsaid battery charger and coupling said first battery to said firstdummyload to discharge said first battery and then recoupling said firstbattery to said battery charger after said first battery is dischargedand then after still another period of time repeats the steps ofuncoupling said second battery from said charger and coupling it to saidsecond dummy load and then back to said charger whereby said firstbattery and said second battery are alternately discharged and chargedperiodically.

8. A battery supply automatic maintenance cycling system as defined inclaim 7 wherein said means responsive to said time measuring meanscomprises a sequencing switch and sensing and reset means coupled tosaid time measuring means.

9. A battery power supply automatic maintenance cycling system asdefined in claim 8 wherein said time coulometer means comprises acoulometer and constant current regulator coupled in series across saidbattery.

10. A battery power supply automatic maintenance cycling system asdefined in claim 9 wherein more than two batteries normally coupledacross said battery charger areprovided and a number of dummy loadsequal in number to the total number of batteries is provided and whereinall said batteries provided are alternately, one at a time, uncoupledfrom said battery charger, coupled to their respective loads fordischarge and then recoupled to said battery charger.

11. A battery power supply automatic maintenance cycling systemcomprising:

a battery having a plurality of cells coupled in series to a batterycharger;

time measuring means coupled to said battery;

a dummy load; and

means responsive to said time measuring means for automaticallyuncoupling all of said cells, alternately, one at a time, from saidcharger and coupling the one cell uncoupled from said charger at thattime to said dummy load to discharge that said cell then recoupling thissaid cell to said battery charger whereby all of said cells arealternately discharged and charged one at a time.

12. A battery power supply automatic maintenance cycling system asdefined in claim 11 wherein said meansresponsive to said time measuringmeans includes a sequencing switch coupled to said time measuring means.

13. A battery power supply automatic maintenance cycling system asdefined in claim 12 wherein said time measuring means comprises acoulometer and constant current regulator coupled across all of saidcells.

14. A battery power supply automatic maintenance cycling system asdefined in claim 13 wherein a discharge monitor is coupled to said dummyload and wherein an indicator for indicating a defective cell is coupledto said discharge monitor.

15. A battery power supply automatic maintenance cycling system asdefined in claim 14 wherein power is available to an external load atall times including the times at which a cell is being discharged.

16. A battery power supply automatic maintenance cycling system asdefined in claim 15 wherein terminals are provided for connecting anumber of said cells to an external load and wherein cell switchingmeans are provided to vary the number of said cells coupled to saidterminals so that a predetermined voltage is available to said externalload, said cell switching means being so designed that one or more cellsare automatically added to the number of cells then coupled to saidterminals when one or more cells become defective, the number of cellsadded being equal in number to the number of defective cells, said cellswitching means responding to a cell under discharge as being adefective cell during discharge, whereby said predetermined voltage isavailable to said external load at all times.

1. A battery power supply automatic maintenance cycling systemcomprising: a battery normally coupled across a battery charger; acoulometer for measuring time coupled to said battery; a dummy load; andmeans responsive to said coulometer for automatically uncoupling saidbattery from said battery charger after a predetermined period of timeand coupling said battery to said dummy load to discharge said batteryand then uncoupling said battery from said dummy load and recouplingsaid battery to said battery charger after said battery has beendischarged for a predetermined period of time that is measured by saidcoulometer.
 2. A battery power supply automatic maintenance cyclingsystem as defined in claim 1 wherein a constant current regulator isconnected in series with said coulometer.
 3. A battery power supplyautomatic maintenance cycling system as defined in claim 2 wherein saidmeans responsive to said coulometer includes a voltage responsive switchcoupled to said battery, said battery charger and said dummy load suchthat said batterY is coupled to said dummy load as long as a voltage isapplied to said switch and is coupled to said battery charger when novoltage is applied to said switch.
 4. A battery power supply automaticmaintenance cycling system as defined in claim 3 wherein said coulometerprovides a first voltage when said battery has been coupled across saidbattery charger for a predetermined period and a second voltage whensaid battery has been coupled across said dummy load for a predeterminedperiod of time and wherein sensing and reset means are coupled betweensaid coulometer and said switch to provide a voltage to said switch touncouple said battery from said battery charger and couple said batteryto said dummy load in response to said first coulometer voltage and toremove said voltage from said switch in response to said secondcoulometer voltage to recouple said battery to said battery charger. 5.A battery power supply automatic maintenance cycling system as definedin claim 4 wherein no power is available to an external load during thetime said battery is coupled to said dummy load.
 6. A battery powersupply automatic maintenance cycling system as defined in claim 5wherein at least one additional battery is connected in parallel withsaid battery.
 7. A battery power supply automatic maintenance cylingsystem comprising: a first battery normally coupled to a batterycharger; a second battery normally coupled to said battery charger; timemeasuring means coupled to said first battery and said second battery; afirst dummy load; a second dummy load; and means responsive to said timemeasuring means for automatically uncoupling said first battery fromsaid battery charger after a predetermined period of time and couplingsaid first battery to said first dummy load to discharge said fristbattery and then uncoupling said first battery from said first dummyload and recoupling said first battery to said battery charger aftersaid first battery has been discharged for a predetermined period oftime that is measured by said time measuring means, and forautomatically uncoupling said second battery from said battery charger apredetermined period of time after said first battery is recoupled tosaid battery charger and coupling said second battery to said seconddummy load to discharge said second battery and then recoupling saidsecond battery to said battery charger after said second battery isdischarged and then after another predetermined period of time againuncoupling said first battery from said battery charger and couplingsaid first battery to said first dummy load to discharge said firstbattery and then recoupling said first battery to said battery chargerafter said first battery is discharged and then after still anotherperiod of time repeats the steps of uncoupling said second battery fromsaid charger and coupling it to said second dummy load and then back tosaid charger whereby said first battery and said second battery arealternately discharged and charged periodically.
 8. A battery supplyautomatic maintenance cycling system as defined in claim 7 wherein saidmeans responsive to said time measuring means comprises a sequencingswitch and sensing and reset means coupled to said time measuring means.9. A battery power supply automatic maintenance cycling system asdefined in claim 8 wherein said time coulometer means comprises acoulometer and constant current regulator coupled in series across saidbattery.
 10. A battery power supply automatic maintenance cycling systemas defined in claim 9 wherein more than two batteries normally coupledacross said battery charger are provided and a number of dummy loadsequal in number to the total number of batteries is provided and whereinall said batteries provided are alternately, one at a time, uncoupledfrom said battery charger, coupled to their respective loads fordischarge and then recoupled to said battery charger.
 11. A batterypower supply automatic maintenance cycliNg system comprising: a batteryhaving a plurality of cells coupled in series to a battery charger; timemeasuring means coupled to said battery; a dummy load; and meansresponsive to said time measuring means for automatically uncoupling allof said cells, alternately, one at a time, from said charger andcoupling the one cell uncoupled from said charger at that time to saiddummy load to discharge that said cell then recoupling this said cell tosaid battery charger whereby all of said cells are alternatelydischarged and charged one at a time.
 12. A battery power supplyautomatic maintenance cycling system as defined in claim 11 wherein saidmeans responsive to said time measuring means includes a sequencingswitch coupled to said time measuring means.
 13. A battery power supplyautomatic maintenance cycling system as defined in claim 12 wherein saidtime measuring means comprises a coulometer and constant currentregulator coupled across all of said cells.
 14. A battery power supplyautomatic maintenance cycling system as defined in claim 13 wherein adischarge monitor is coupled to said dummy load and wherein an indicatorfor indicating a defective cell is coupled to said discharge monitor.15. A battery power supply automatic maintenance cycling system asdefined in claim 14 wherein power is available to an external load atall times including the times at which a cell is being discharged.
 16. Abattery power supply automatic maintenance cycling system as defined inclaim 15 wherein terminals are provided for connecting a number of saidcells to an external load and wherein cell switching means are providedto vary the number of said cells coupled to said terminals so that apredetermined voltage is available to said external load, said cellswitching means being so designed that one or more cells areautomatically added to the number of cells then coupled to saidterminals when one or more cells become defective, the number of cellsadded being equal in number to the number of defective cells, said cellswitching means responding to a cell under discharge as being adefective cell during discharge, whereby said predetermined voltage isavailable to said external load at all times.